Electronic displays are now being used for not only indoor entertainment purposes, but are now being utilized for indoor and outdoor advertising/informational purposes. For example, liquid crystal displays (LCDs), plasma displays, light emitting diode (LED), electroluminescence, light-emitting polymers, organic light emitting diode displays (OLEDs) and many other displays can now be used to display information and advertising materials to consumers in locations outside of their own home or within airports, arenas, transit stations, stadiums, restaurants/bars, gas station pumps, billboards, and even moving displays on the tops of automobiles or on the sides of trucks.
The rapid development of these displays has allowed users to mount them in a variety of locations that were not previously available. Further, the popularity of high definition (HD) television has increased the demand for larger and brighter displays, especially large displays which are capable of producing HD video. The highly competitive field of consumer advertising has also increased the demand for large, attention-grabbing, bright displays.
When used outdoors, high ambient temperatures and solar loading can present several thermal-regulatory issues. When a display is exposed to direct sunlight this can increase the temperature of the display dramatically due to the solar loading of the front display surface due to the radiative heat of the sun. It has been found, that moving air through a gap between the exterior transparent plate and the image assembly can sometimes provide adequate cooling of the display assembly. Further, when producing an image with a display that has been placed in direct sunlight, the illumination of the display assembly must overcome the high ambient light levels. Thus, the display must be very bright and sometimes produce high levels of illumination which can generate high levels of heat coming from the image assembly (or backlight if necessary). This heat must be removed from the display or it may damage the electrical assemblies. If an LCD is used, high internal temperatures can cause the liquid crystal material to malfunction and may produce noticeable failures on the image. LEDs can degrade in performance and efficiency when exposed to high temperatures. Other technologies (OLED, light-emitting polymers, etc.) can also malfunction when exposed to high temperatures.